Making micro-wire electrode structure with single-layer dummy micro-wires

ABSTRACT

A method of making a micro-wire electrode structure includes providing a substrate having a surface. A plurality of first micro-wire electrodes spatially separated by first electrode gaps is located in a first layer in relation to the surface, each first micro-wire electrode including a plurality of electrically connected first micro-wires. A plurality of electrically isolated second micro-wire electrodes in a second layer is located in relation to the surface, the second layer at least partially different from the first layer and each second micro-wire electrode including a plurality of electrically connected second micro-wires. A plurality of first gap micro-wires is located in each first electrode gap, at least some of the first gap micro-wires located in a gap layer different from the first layer, the first gap micro-wires electrically isolated from the first micro-wires.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is made to commonly-assigned co-pending U.S. patentapplication Ser. No. ______ (Attorney Docket No. K001713USO1RLO) filedconcurrently herewith, entitled Micro-Wire Electrode Structure withSingle-Layer Dummy Micro-Wires, by Cok, the disclosure of which isincorporated herein.

Reference is made to commonly-assigned co-pending U.S. patentapplication Ser. No. 14/032,213, filed Sep. 20, 2013 entitled Micro-WireTouch Screen with Unpatterned Conductive Layer, by Burberry et al.; andto commonly-assigned co-pending U.S. patent application Ser. No.14/1677,134, filed Jan. 29, 2014. entitled Micro-Wire Electrodes withEqui-Potential Dummy Micro-Wires, by Cok; the disclosures of which areincorporated herein.

FIELD OF THE INVENTION

The present invention relates to touch screens having micro-wireelectrodes and an unpatterned transparent conductor layer.

BACKGROUND OF THE INVENTION

Transparent conductors are widely used in the flat-panel displayindustry to form electrodes that are used to electrically switchlight-emitting or light-transmitting properties of a display pixel, forexample in liquid crystal or organic light-emitting diode displays.Transparent conductive electrodes are also used in touch screens inconjunction with displays. In such applications, the transparency andconductivity of the transparent electrodes are important attributes. Ingeneral, it is desired that transparent conductors have a hightransparency (for example, greater than 90% in the visible spectrum) anda low electrical resistivity (for example, less than 10 ohms/square).

Transparent conductive metal oxides are well known in the display andtouch-screen industries and have a number of disadvantages, includinglimited transparency and conductivity and a tendency to crack undermechanical or environmental stress. Typical prior-art conductiveelectrode materials include conductive metal oxides such as indium tinoxide (ITO) or very thin layers of metal, for example, silver oraluminum or metal alloys including silver or aluminum. These materialsare coated, for example, by sputtering or vapor deposition, and arepatterned on display or touch-screen substrates, such as glass. Forexample, the use of transparent conductive oxides to form arrays oftouch senses on one side of a substrate is taught in U.S. PatentApplication Publication No. 2011/0099805 entitled “Method of FabricatingCapacitive Touch-Screen Panel”.

Transparent conductive metal oxides are increasingly expensive andrelatively costly to deposit and pattern. Moreover, the substratematerials are limited by the electrode material deposition process (suchas sputtering) and the current-carrying capacity of such electrodes islimited, thereby limiting the amount of power that is supplied to thepixel elements and the size of touch screens that employ suchelectrodes. Although thicker layers of metal oxides or metals increaseconductivity, they also reduce the transparency of the electrodes.

Apparently transparent electrodes including very fine patterns ofconductive elements, such as metal wires or conductive traces are known.For example, U.S. Patent Application Publication No. 2011/0007011teaches a capacitive touch screen with a mesh electrode, as do U.S.Patent Application Publication No. 2010/0026664, U.S. Patent ApplicationPublication No. 2010/0328248, and U.S. Pat. No. 8,179,381, which arehereby incorporated in their entirety by reference. As disclosed in U.S.Pat. No. 8,179,381, fine conductor patterns are made by one of severalprocesses, including laser-cured masking, inkjet printing, gravureprinting, micro-replication, and micro-contact printing. In particular,micro-replication is used to form micro-conductors formed inmicro-replicated channels. The apparently transparent micro-wireelectrodes include micro-wires between 0.5μ and 4μ wide and atransparency of between approximately 86% and 96%.

Conductive micro-wires are formed in micro-channels embossed in asubstrate, for example as taught in CN102063951, which is herebyincorporated by reference in its entirety. As discussed in CN102063951,a pattern of micro-channels are formed in a substrate using an embossingtechnique. Embossing methods are generally known in the prior art andtypically include coating a curable liquid, such as a polymer, onto arigid substrate. A pattern of micro-channels is embossed (impressed orimprinted) onto the polymer layer by a master having an inverted patternof structures formed on its surface. The polymer is then cured. Aconductive ink is coated over the substrate and into the micro-channels,the excess conductive ink between micro-channels is removed, forexample, by mechanical buffing, patterned chemical electrolysis, orpatterned chemical corrosion. The conductive ink in the micro-channelsis cured, for example, by heating. In an alternative method described inCN102063951, a photosensitive layer, chemical plating, or sputtering isused to pattern conductors, for example, using patterned radiationexposure or physical masks. Unwanted material (such as photosensitiveresist) is removed, followed by electro-deposition of metallic ions in abath.

Mutual capacitive touch screen devices are constructed by locating driveelectrodes near sense electrodes to form an electric field. In oneprior-art design, the drive and sense electrodes are located on a commonsubstrate with bridge electrical connections to prevent electricalshorts between the drive and sense electrodes where the drive electrodescross over or under the sense electrodes. In another prior-art design,the drive and sense electrodes are located on either side of adielectric layer. Referring to FIG. 11, a prior-art display andtouch-screen apparatus 100 includes a display 110 with a correspondingtouch screen 120 mounted with the display 110 so that informationdisplayed on the display 110 can be viewed through the touch screen 120.Graphic elements displayed on the display 110 are selected, indicated,or manipulated by touching a corresponding location on the touch screen120. The touch screen 120 includes a first transparent substrate 122with transparent first electrodes 130 extending in the x dimension onthe first transparent substrate 122 and a second transparent substrate126 with transparent second electrodes 132 extending in the y dimensionfacing the x-dimension transparent first electrodes 130 on the secondtransparent substrate 126. A dielectric layer 124 is located between thefirst and second transparent substrates 122, 126 and transparent firstand second electrodes 130, 132. Touch pad areas 128 are formed by theoverlap of the transparent first electrodes 130 with the transparentsecond electrodes 132. When a voltage is applied across the transparentfirst and second electrodes 130, 132, electric fields are formed betweenthem that are measurable to detect changes in capacitance due to thepresence of a touch element, such as a finger or stylus.

A display controller 142 connected through electrical bus connections136 controls the display 110 in cooperation with a touch-screencontroller 140. The touch-screen controller 140 is connected throughelectrical bus connections 136 and wires 134 and controls the touchscreen 120. The touch-screen controller 140 detects touches on the touchscreen 120 by sequentially electrically energizing and testing theapparently transparent x-dimension first and y-dimension secondelectrodes 130, 132.

Referring to FIG. 12 as well as FIG. 11, in another prior-artembodiment, the rectangular transparent first electrodes 130 separatedby first electrode gaps 60 and transparent second electrodes 132separated by second electrode gaps 62 include micro-wires 150 and arearranged orthogonally in a micro-pattern 156 on transparent first andsecond substrates 122, 126 with intervening dielectric layer 124,forming touch screen 120 which, in combination with the display 110forms the touch screen 120 and display and touch screen apparatus 100.

As is known in the prior art, electromagnetic interference from thedisplay 110 can interfere with the operation of the touch-screen 120.This problem is mitigated by providing a ground plane between the touchscreen 120 and display 110. However, such a structure undesirablyincreases the thickness and decreases the transparency of the displayand touch screen apparatus 100.

Alternatively, it has been recognized that shielding is achieved bycontrolling the relative width of the drive and sense electrodes. Forexample U.S. Pat. No. 7,920,129 discloses a multi-touch capacitivetouch-sense panel created using a substrate with column and row tracesformed on either side of the substrate. To shield the column (sense)traces from the effects of capacitive coupling from a modulated V_(com)layer in an adjacent liquid crystal display (LCD) or any source ofcapacitive coupling, the row traces were widened to shield the columntraces, and the row (drive) traces were placed closer to the LCD. Inparticular, the rows are widened so that there is spacing of about 30microns between adjacent row traces. In this manner, the row traces canserve the dual functions of driving the touch sense panel, and also thefunction of shielding the more sensitive column (sense) traces from theeffects of capacitive coupling.

Shielding has also been achieved by using metal micro-wire senseelectrodes in combination with transparent conductive drive electrodes.For example U.S. Pat. No. 8,279,187 discloses a multi-layer touch panelhaving an upper electrode layer having a plurality of compositeelectrodes including a plurality of metal or metal alloy micro-wireconductors with a cross-sectional dimension of less than 10 microns, alower electrode layer having a plurality of (patterned) indiumoxide-based electrodes, the upper electrodes and lower electrodesdefining an electrode matrix having nodes where the upper and lowerelectrodes cross over. The upper electrode layer is disposed between thefirst layer and the lower electrode layer and a dielectric layer isdisposed between the upper electrode layer and the lower electrodelayer. As noted above, it is difficult, expensive, or impossible to meetconductivity requirements for larger touch-screens using patternedindium tin oxide electrodes.

In general, touch screens are intended to be invisible to a user. It isimportant, therefore, that any conductive structures in a touch screenbe visually imperceptible. In prior-art designs, apparently transparentconductive electrodes made of transparent conductive oxides reduceelectrode visibility. Nonetheless, such electrodes do absorb some light,having a transparency for example of 88% in the visible range and aslightly yellow appearance. Thus, electrode structures in a touch screenhaving transparent conductive oxides are visible to perceptive users. Inparticular, regular first electrode gaps 60 between transparent firstelectrodes 130 and second electrode gaps 62 between transparent secondelectrodes 132 are visible as areas with increased transparency.

Referring to FIG. 13, to reduce the visibility of gaps betweenelectrodes in a touch screen, dummy conductive structures are providedin the first electrode gap 60. These dummy structures typically includeconductive materials and structures similar to those found in theelectrodes but are not electrically connected to the electrodes. Thus,the dummy structures provide optical uniformity in the touch screen byproviding structures with an appearance similar to the electrodes butwithout any electrical function. Micro-wire breaks 64 or otherconductive element breaks between the dummy structures and theelectrodes to maintain electrical isolation between the dummy structuresand the electrodes are typically so small (for example, a few microns)that the micro-wire breaks 64 are imperceptible to viewers. As shown inFIG. 13, a plurality of rectangular, spatially separated transparentfirst electrodes 130 connected to wires 134 in an electrical busconnection 136 are arranged in an array on a first transparent substrate122. Each transparent first electrode 130 includes a plurality ofelectrically connected micro-wires 150. Dummy micro-wires 152 located infirst electrode gaps 60 between the transparent first electrodes 130 arearranged in a similar way so that the dummy micro-wires 152 located inthe first electrode gaps 60 between the transparent first electrodes 130appear similar to the micro-wires in transparent first electrodes 130.

U.S. Patent Application Publication No. 2011/0248953 entitled “TouchScreen Panel” describes conductive dummy patterns between adjacentsensing cells in a touch screen panel. U.S. Patent ApplicationPublication No. 2011/0289771 entitled “Method for Producing ConductiveSheet and Method for Producing Touch Panel” describes unconnected dummypatterns formed near each side of a sensing region. U.S. Pat. No.7,663,607 entitled “Multi-Point Touch Screen” describes dummy featuresdisposed between driving lines and sensing lines to optically improvethe visual appearance of the touch screen. The dummy features providethe touch screen with a more uniform appearance and are electricallyisolated and positioned in the gaps between each of the lines. Althoughthey can be patterned separately, the dummy features are typicallypatterned along with the lines and formed with the same conductivematerials. The dummy features still produce some gaps but the gaps aremuch smaller than the gaps found between the lines.

SUMMARY OF THE INVENTION

There remains a need for further improvements in the structure of adisplay and touch-screen apparatus that improves sensitivity andefficiency, reduces susceptibility to electromagnetic interference, andimproves optical uniformity.

In accordance with the present invention, a method of making amicro-wire electrode structure comprises:

providing a substrate having a surface;

locating a plurality of first micro-wire electrodes spatially separatedby first electrode gaps in a first layer in relation to the surface,each first micro-wire electrode including a plurality of electricallyconnected first micro-wires;

locating a plurality of electrically isolated second micro-wireelectrodes in a second layer in relation to the surface, the secondlayer at least partially different from the first layer and each secondmicro-wire electrode including a plurality of electrically connectedsecond micro-wires; and

locating a plurality of first gap micro-wires in each first electrodegap, at least some of the first gap micro-wires located in a gap layerdifferent from the first layer, the first gap micro-wires electricallyisolated from the first micro-wires.

The present invention provides a micro-wire electrode structure usefulin capacitive touch screens having improved sensitivity, efficiency,consistency, optical uniformity, and reduced susceptibility toelectromagnetic interference. By locating dummy micro-wires from onelayer in another layer, electrode electrical performance is improved andoptical uniformity maintained or improved.

The presence of an unpatterned conductive layer electrically connectedto first electrodes and first micro-wires provides electromagneticshielding to the first and second electrodes, thereby reducingelectromagnetic interference. The integrated unpatterned conductivelayer therefore reduces device thickness by reducing the number ofinsulating layers. This has the additional benefit of reducingconductive layer thickness and improving transparency in comparison to aconventional shielding system.

The presence of the unpatterned conductive layer also increasescapacitance between the first and second electrodes, thereby reducingthe voltage needed to sense changes in the capacitive field, for exampledue to touches, thereby improving efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent when taken in conjunction with the followingdescription and drawings wherein identical reference numerals have beenused to designate identical features that are common to the figures, andwherein:

FIGS. 1A, 1B, and 1C are plan views of different layers of a micro-wireelectrode structure according to an embodiment of the present invention;

FIG. 1D is a perspective combining the layers of FIGS. 1A, 1B, and 1C;

FIGS. 2A, 2B and 2C are plan views of the same layer of a micro-wireelectrode structure with different micro-wire markings according toanother embodiment of the present invention;

FIG. 2C is a plan view of a layer of a micro-wire electrode structureaccording to another embodiment of the present invention;

FIG. 2D is a perspective combining the layers of FIGS. 2A, 2B, and 2C;

FIG. 3A is a plan view of a layer of a micro-wire electrode structureaccording to yet another embodiment of the present invention;

FIGS. 3B and 3C are plan views of the same layers of a micro-wireelectrode structure with different micro-wire markings according to yetanother embodiment of the present invention;

FIG. 3D is a plan view of a layer of a micro-wire electrode structureaccording to yet another embodiment of the present invention;

FIGS. 3E and 3F are perspectives combining the layers of FIGS. 3A, 3B,3C and 3D, in different embodiments of the present invention;

FIGS. 4A and 4B are plan views of the same layer of a micro-wireelectrode structure with different micro-wire markings according to afurther embodiment of the present invention;

FIGS. 4C and 4D are plan views of different layers of a micro-wireelectrode structure according to a further embodiment of the presentinvention;

FIGS. 5 and 6 are cross sectional views of different embodiments of thepresent invention;

FIGS. 7-10 are flow diagrams illustrating various methods of variousembodiments of the present invention;

FIG. 11 is a prior-art perspective of a capacitive touch screen;

FIG. 12 is a plan view of two prior-art overlapping micro-wireelectrodes useful in understanding the present invention;

FIG. 13 is a schematic illustrating prior-art micro-wire electrodes anddummy micro-wires useful in understanding the present invention; and

FIG. 14 is a cross sectional view of yet another embodiment of thepresent invention.

The Figures are not drawn to scale since the variation in size ofvarious elements in the Figures is too great to permit depiction toscale.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a micro-wire electrode structure usefulin forming capacitive touch-screen devices and in combination with adisplay. The micro-wire electrode structure improves electrodeconductivity, optical uniformity, reduces the effects of electromagneticinterference, and improves touch-response sensitivity, efficiency, andconsistency over the extent of the touch screen. The micro-wireelectrode structure of the present invention is also useful in otherapplications requiring overlapping micro-wire electrodes and is notlimited to applications of touch-screen devices. According toembodiments of the present invention, dummy wires provided for opticaluniformity found in layers of conventional prior-art designs are insteadused in different layers to improve electrode conductivity or resistanceto electromagnetic interference.

FIGS. 1A, 1B, and 1C are plan views of layers forming a multi-layerstructure. The layers are shown in combination in the perspective ofFIG. 1D. Referring to FIG. 1D, a micro-wire electrode structure 5includes a substrate 10 with first and second opposing sides, one ofwhich provides a surface 12. In various embodiments, the substrate 10 isan element of a display 110, for example a cover or substrate of thedisplay 110, or is affixed to the display 110. In an embodiment, thedisplay 110 is a source of electromagnetic radiation located on oradjacent to the second opposing side.

As shown in FIGS. 1A and 1D, a plurality of electrically isolated firstmicro-wire electrodes 22 spatially separated by first electrode gaps 60is located in a first layer 20 in relation to the surface 12. Each firstmicro-wire electrode 22 includes a plurality of electrically connectedfirst micro-wires 24. The first electrode gaps 60 electrically isolateeach of the first micro-wire electrodes 22 from the other firstmicro-wire electrodes 22 and each first micro-wire electrode 22 isconnected to one of the wires 134 for controlling the first micro-wireelectrode 22.

Referring to FIGS. 1B and 1D, a plurality of electrically isolatedsecond micro-wire electrodes 52 is located in a second layer 50 inrelation to the surface 12. The second layer 50 is at least partiallydifferent from the first layer 20. Each second micro-wire electrode 52includes a plurality of electrically connected second micro-wires 54.Micro-wire breaks 64 electrically isolate each of the second micro-wireelectrodes 52 from the other second micro-wire electrodes 52 and eachsecond micro-wire electrode 52 is connected to one of the wires 134 forcontrolling the second micro-wire electrode 52.

Referring to FIGS. 1C and 1D, a plurality of first gap micro-wires 26 islocated in each first electrode gap 60 in a gap layer 80 different fromthe first layer 20 (FIG. 1A). The first micro-wires 24 (FIG. 1A) and thefirst gap micro-wires 26 have the same pattern (ignoring the micro-wirebreaks 64). The first gap micro-wires 26 are electrically isolated fromthe first micro-wires 24 in first micro-wire electrodes 22. In anembodiment, the first gap micro-wires 26 include micro-wire breaks 64,as described further below. In an embodiment, the first gap micro-wires26 have the same micro-wire pattern over the touch-sensitive area 32(FIGS. 1A-1C) as the first micro-wires 24 so as to provide a uniformoptical appearance. In this embodiment, the first gap micro-wires 26serve as dummy micro-wires to visually fill in the first electrode gaps60 between the first micro-wire electrodes 22 and provide opticaluniformity in the first electrode gaps 60.

As shown in FIGS. 1A, 1B, and 1C, the first and second micro-wireelectrodes 22, 52 overlap in a touch-sensitive area 32. The overlappingportions of the first and second micro-wire electrodes 22, 52 formcapacitors whose capacitance is detectably modified by the presence of atouching implement, such as a finger, to form a touch-screen device.

In an embodiment, the first and second micro-wires 24, 54 are formed ina regular micro-wire pattern that extends over the touch-sensitive area32. In useful designs, the first electrode gaps 60 are readily visibleto the unaided human visual system where the micro-wire breaks 64 arenot when viewed at useful distances. For example, the first electrodegaps 60 are 10-1,000 microns wide and the micro-wire breaks 64 are0.1-10 microns wide.

As shown in FIG. 1D with respect to the present invention, first gapmicro-wires 26 that are described as located within the first electrodegap 60 are located within the first electrode gap 60 when viewed from adirection P perpendicular to the surface 12 so that the first gapmicro-wires 26 appear between the first electrode gaps 60. The firstelectrode gap 60 extends through multiple layers in the direction P. Asnoted, the first gap micro-wires 26 are in a separate gap layer 80 thatis different from the first layer 20 in the first electrode gap 60 butare not in the first layer 20. Thus, as shown in FIG. 1D, the first gapmicro-wires 26 are located in the first electrode gaps 60 because, asviewed from the direction P perpendicular to the surface 12, the firstgap micro-wires 26 appear between the first micro-wire electrodes 22. Infurther embodiments, the first micro-wire electrodes 22 extend in afirst direction D1 parallel to the surface 12, the second micro-wireelectrodes 52 extend in a second direction D2 parallel to the surface 12and the first direction D1 is orthogonal to the second direction D2.

Referring to FIGS. 2A, 2B, 2C and 2D, in another embodiment of thepresent invention, the gap layer 80 is the second layer 50, the firstgap micro-wires 26 are located within the second micro-wire electrodes52, and at least some of the first gap micro-wires 26 are electricallyconnected to the second micro-wires 54. FIGS. 2A, 2B and 2C, are planviews of layers forming a multi-layer structure. The layers are shown incombination in the perspective of FIG. 2D.

As shown in FIG. 2D, the second layer 50 and the gap layer 80 are thesame layer in relation to the surface 12 of the substrate 10 and display110. The second layer 50 includes both the second micro-wires 54 and atleast some of the first gap micro-wires 26 in second micro-wireelectrodes 52. The second micro-wire electrodes 52 are electricallyisolated from each other by the micro-wire breaks 64 in the first gapmicro-wires 26, as illustrated in FIGS. 1A, 2A, 2B and 2C. The firstmicro-wire electrodes 22 with the first micro-wires 24 separated byfirst electrode gaps 60 are formed in a first layer 20 different fromthe second layer 50 and gap layer 80. The embodiment of FIGS. 2A, 2B, 2Cand 2D provides an electrical advantage in that the second micro-wireelectrodes 52 have improved electrical conductivity because the firstgap micro-wires 26 are located within the second micro-wire electrodes52 and are electrically connected to the second micro-wires 54, as shownin FIGS. 2A and 2B

FIG. 2A illustrates both the second micro-wire electrodes 52 and thefirst gap micro-wires 26 in the second layer 50 so that the second layer50 is also the gap layer 80. The first gap micro-wires 26 are in thefirst electrode gap 60. The second micro-wires 54 of the secondmicro-wire electrodes 52 are shown with solid lines and the first gapmicro-wires 26 are shown with dashed lines. Because the second layer 50includes both the second micro-wires 54 and at least some of the firstgap micro-wires 26, the second micro-wires 54 and at least some of thefirst gap micro-wires 26 are electrically connected to form secondmicro-wire electrodes 52 having a variable micro-wire density along thelength of the second micro-wire electrodes 52. Note that the micro-wirebreaks 64 illustrated in FIG. 1C in this embodiment electrically isolateeach of the second micro-wire electrodes 52 from the other secondmicro-wire electrodes 52.

The elements and structures illustrated in FIG. 2B are identical tothose of FIG. 2A. The only difference in the Figures is that the firstgap micro-wires 26 are shown in FIG. 2B with solid lines as are thesecond micro-wires 54 of the second micro-wire electrodes 52 separatedby the micro-wire breaks 64 in the first gap micro-wires 26 in the firstelectrode gap 60. Both the first gap micro-wires 26 and the secondmicro-wires 54 are in the second layer 50 (which is also the gap layer80).

Referring next to the plan view of FIG. 2C, the first micro-wireelectrodes 22 and the first micro-wires 24 separated by the firstelectrode gaps 60 are added to the illustration of FIG. 2B to illustratethe micro-wire electrode structure 5. The first micro-wires 24 of thefirst micro-wire electrodes 22 (illustrated in FIG. 1A) are shown withdashed lines to distinguish them from the second micro-wires 54 and thefirst gap micro-wires 26 of the second micro-wire electrodes 52. Thefirst micro-wire electrodes 22 are separated by the first electrode gaps60 and the second micro-wire electrodes 52 are separated by themicro-wire breaks 64 in the first gap micro-wires 26. Thus, in FIG. 2C,the micro-wires illustrated with solid lines are those of the secondlayer 50 and the micro-wires illustrated with the dashed lines are thoseof the first layer 20 (see also FIG. 2D). The first and secondmicro-wire electrodes 22, 52 overlap in the touch-sensitive area 32 toform capacitors useful in a capacitive touch screen.

As shown in FIG. 2C, the second micro-wire electrodes 52 are separatedby the micro-wire breaks 64 in the first gap micro-wires 26 butotherwise have the same micro-wire pattern as the first micro-wires 24and first gap micro-wires 26 (and the first micro-wire electrode 22)except that the second micro-wires 54 are spatially offset in onedimension in a direction parallel to the surface and are 180 degreesspatially out of phase with respect to the first micro-wires 24.

The embodiment of FIGS. 2A, 2B, 2C and 2D provides an electricaladvantage in that the second micro-wire electrodes 52 have improvedelectrical conductivity because the first gap micro-wires 26 of thefirst electrode gap 60 are connected to the second micro-wires 54 of thesecond micro-wire electrodes 52 (FIG. 2B). Furthermore, the presence ofadditional first gap micro-wires 26 in the second micro-wire electrodes52 reduces the interference of electromagnetic radiation arising fromsources below the second layer 50 (e.g. the display 110) on the firstmicro-wire electrodes 22. Thus, if the first micro-wire electrodes 22are used as sense electrodes and the second micro-wire electrodes 52 areused as drive electrodes in a capacitive touch screen, the senseelectrode (first micro-wire electrodes 22) have reduced noise andinterference and improved sensitivity.

FIGS. 1A, 1C, 3A, 3B, 3C and 3D are plan views of layers forming amulti-layer structure according to embodiments of the present invention.The layers are shown in different combinations in the perspectives ofFIGS. 3E and 3F. As noted above, the second gap micro-wires 56 (FIGS.3A-3D) are located in each second electrode gap 62 when viewed from adirection orthogonal to the surface 12 (FIG. 1D) and are not necessarilyin a common layer with the second micro-wires 54 and second micro-wireelectrodes 52.

Referring next to FIG. 3A, in another embodiment the second micro-wireelectrodes 52 having the second micro-wires 54 are spatially separatedby second electrode gaps 62. A plurality of second gap micro-wires 56are located in each second electrode gap 62 and the second gapmicro-wires 56 are electrically isolated from the second micro-wires 54by the micro-wire breaks 64. The second gap micro-wires 56 have the samemicro-pattern as the second micro-wires 54, ignoring the micro-wirebreaks 64.

Referring next to FIG. 3B, the first gap micro-wires 26 illustrated inFIG. 1C are located in the second layer 50 of FIG. 3A, have a commonmicro-pattern with the second micro-wires 54 and second gap micro-wires56, and at least some of the first gap micro-wires 26 are electricallyconnected to the second micro-wires 54. The first gap micro-wires 26that are within the area defined by the second micro-wire electrodes 52are electrically connected to the second micro-wires 54 of the secondmicro-wire electrode 52. The first gap micro-wires 26 that are notwithin the area defined by the second micro-wire electrodes 52 are notelectrically connected to the second micro-wires 54 or the secondmicro-wire electrode 52. Instead, they are located in the secondelectrode gap 62 and, in an embodiment, are electrically connected tothe second gap micro-wires 56.

In FIG. 3B, the second micro-wires 54 and the second gap micro-wires 56are shown with solid lines. The first gap micro-wires 26 are shown withdashed lines. Because the first gap micro-wires 26 in the secondelectrodes 52 are electrically connected to the second micro-wires 54they form a single electrode with variable micro-wire density. Likewise,because the first gap micro-wires 26 in the second electrode gap 62 areelectrically connected to the second gap micro-wires 56, they form asingle electrically conductive structure with variable micro-wiredensity. The first gap micro-wires 26 in the first electrode gap 60 andthe second micro-wires 54 of the second micro-wire electrodes 52 areelectrically isolated from the first gap micro-wires 26 in the firstelectrode gap 60 and the second gap micro-wires 56 in the secondelectrode gaps 62 by micro-wire breaks 64.

FIG. 3C illustrates the identical elements and structures illustrated inFIG. 3B. The only difference is that the first gap micro-wires 26 in thefirst electrode gaps 60 are now shown with solid lines as are the secondmicro-wires 54 of the second micro-wire electrodes 52 and the second gapmicro-wires 56 in the second electrode gap 62. Both the first gapmicro-wires 26 and the second micro-wires 54 are in the second layer 50(which is also the gap layer 80).

Referring next to FIG. 3D, the first micro-wires 24 of the firstmicro-wire electrodes 22 separated by first electrode gaps 60 (FIG. 1A)are incorporated into the micro-wire structure of FIG. 3C to form amicro-wire electrode structure 5. In this illustration of the micro-wireelectrode structure 5, the first micro-wires 24 are shown with dashedlines corresponding to the first layer 20 (e.g. as in FIG. 2D). Thefirst gap micro-wires 26, the second micro-wires 54 of the secondmicro-wire electrodes 52 separated by second electrode gaps 62, and thesecond gap micro-wires 56 are shown with solid lines. The first gapmicro-wires 26 and the second micro-wires 54 of the second micro-wireelectrodes 52 are electrically connected to form an electrode withvariable micro-wire density (as shown more clearly in FIG. 3C that hasimproved conductivity and performance. The second gap micro-wires 56 areelectrically connected to first gap micro-wires 26 in the secondelectrode gap 62 providing variable-density dummy micro-wires that morereadily shields electromagnetic radiation.

FIG. 3E is a perspective of a combination of the layers shown in FIG.3D. In the embodiment of FIG. 3E, the second layer 50 (also the gaplayer 80) is between the first layer 20 and the surface 12 of substrate10 and display 110. If the display 110 creates electromagneticinterference, according to an embodiment of the present invention, thefirst gap micro-wires 26 (FIG. 3D) in the second micro-wire electrodes52 and the second electrode gap 62 shield the first micro-wireelectrodes 22 in the first layer 20 separated by the first electrodegaps 60. The micro-wire breaks 64 prevent electrical shorts between thesecond micro-wire electrodes 52. Thus, signals sensed by the firstmicro-wire electrodes 22 have an improved signal-to-noise ratio. Aseparate dielectric layer 40 is provided to separate the first andsecond micro-wire electrodes 22, 52. If the first layer 20 and secondlayer 50 are otherwise electrically isolated (for example by portions ofthe first or second layers 20, 50 as discussed further below), thedielectric layer 40 is unnecessary.

In the embodiment illustrated in the perspective of FIG. 3F, the firstlayer 20 is between the second layer 50 (which is also the gap layer 80)and the surface 12 of substrate 10 and the display 110. An unpatternedconductive layer 30 is in electrical contact with the first micro-wires24 (FIG. 3D) of the first micro-wire electrodes 22 separated by firstelectrode gaps 60. A separate optional dielectric layer 40 is providedto separate the first micro-wire electrodes 22 from the secondmicro-wire electrodes 52 and the unpatterned conductive layer 30 fromthe second electrodes 52 separated by second electrode gaps 62. Thefirst and second micro-wire electrodes 22, 52 extend in directionsorthogonal to those of FIG. 3E. In general, the positions of the firstand second layers 20, 50 and the orientations and positions of the firstand second micro-wire electrodes 22, 52 can be interchanged.

The unpatterned conductive layer 30 is an electrically conductive layerwith a relatively high resistance compared to the first micro-wires 24and the first micro-wire electrodes 22 and is unpatterned within thetouch-sensitive area 32 (FIG. 1A, 2C, 2D) so that at least someelectrical current can flow from one first micro-wire electrode 22 toanother first micro-wire electrode 22 through the unpatterned conductivelayer 30. Thus, the first micro-wire electrodes 22 are not completelyelectrically isolated from each other. If the display 110 createselectromagnetic interference, according to an embodiment of the presentinvention the unpatterned conductive layer 30 shields the secondmicro-wire electrodes 52 in the second layer 50. Thus, signals sensed bythe second micro-wire electrodes 52 have an improved signal-to-noiseratio. In embodiments, the unpatterned conductive layer 30 is patternedin areas outside the touch-sensitive area 32, for example around theperiphery of a touch screen.

In the embodiment illustrated in FIGS. 3A-3F, the first gap micro-wires26 and the second gap micro-wires 56 are located in the second layer 50.In another embodiment, at least some of the second gap micro-wires 56are located in a layer different from the second layer 50.

FIGS. 4A, 4B, 4C and 4D are plan views of various layers of a micro-wireelectrode structure 5 in various embodiments of the present invention.Combinations of the layers are shown in FIGS. 3E and 3F.

Referring first to FIG. 4A, the elements of FIG. 3A are combined withthe elements of FIG. 1C to form the micro-wire electrode structure 5 ofan embodiment of the present invention. As shown in FIG. 4A, the firstgap micro-wires 26 in the first electrode gaps 60 between the firstmicro-wire electrodes 22 (FIG. 1A) are illustrated with dashed lines andthe second micro-wires 54 and the second gap micro-wires 56 in thesecond electrode gap 62 between the second micro-wire electrodes 52 areillustrated with solid lines.

FIG. 4B illustrates the identical elements and structures illustrated inFIG. 4A. The only differences are that the first gap micro-wires 26 arenow shown with solid lines representing the second layer 50 (FIG. 3E) asare the second micro-wires 54 of the second micro-wire electrodes 52.The second gap micro-wires 56 in the first micro-wire electrodes 22(FIG. 1A) are now shown as dashed lines representing the first layer 20(FIG. 3E). The second gap micro-wires 56 shown as dashed lines no longerinclude micro-wire breaks 64 with the first micro-wires 24 (FIG. 1A)since, as shown in FIG. 4C, the dashed second gap micro-wires 56 are ina different layer from the second micro-wires 54 and the second gapmicro-wires 56 in the first electrode gap 60 and therefore will maintainelectrical isolation between the second micro-wire electrodes 52. Theabsence of the micro-wire breaks 64 improves both optical uniformity andresistance to electromagnetic radiation interference.

FIG. 4C illustrates the structure of FIG. 4B with the addition of thefirst microwire electrodes 22 and the first micro-wires 24. In thisFigure, the first micro-wires 24 of the first micro-wire electrodes 22and the second gap micro-wires 56 in the area of the first micro-wireelectrodes 22 that are not in both the first and second electrode gaps60, 62 are shown with dashed lines that correspond to first micro-wireelectrodes 22 in the first layer 20 (FIGS. 3E and 3F) and are separatelyshown in FIG. 4D. FIG. 4D shows the first micro-wire electrodes 22 withthe first micro-wires 24 and the second gap micro-wires 56 in the areaof the first micro-wire electrodes 22 forming the first micro-wireelectrodes 22 with variable micro-wire density.

As shown in FIG. 4C, the second micro-wires 54 and the first gapmicro-wires 26 of the second micro-wire electrodes 52 are shown withsolid lines. The first and second gap micro-wires 26, 56 in both thefirst and second electrode gaps 60, 62 are also shown with solid lines.Solid-line micro-wires correspond to the second layer 50 (FIGS. 3E and3F). Both the dielectric layer 40 (FIGS. 3E and 3F) and the unpatternedconductive layer 30 (FIG. 3F) are useful with the layers illustrated inFIG. C in the structures illustrated in either FIG. 3E or FIG. 3F.

The micro-wire electrode structure 5 of FIG. 4C electrically connectsthe first gap micro-wires 26 that are in the area of the secondmicro-wire electrodes 52 to the second micro-wires 54 to form moreconductive second micro-wire electrodes 52 (shown in FIG. 4B).Similarly, the second gap micro-wires 56 that are in the area of thefirst micro-wire electrodes 22 are electrically connected to the firstmicro-wires 24 (as shown in FIG. 4D). Those first gap micro-wires 26 andsecond gap micro-wires 56 that are in neither of the areas of the firstor second micro-wire electrodes 22, 52 and are therefore in both thefirst and second electrode gaps 60, 62, shown as dummy-wire area 36, areelectrically connected and can serve as an electromagnetic interferenceshield for the first or second micro-wire electrodes 22, 52. Thus, atleast some of the dummy micro-wires of the first layer 20 (first gapmicro-wires 26) serve as second micro-wire electrode 52 micro-wires.Likewise, at least some of the dummy micro-wires of the second layer 50(second gap micro-wires 56) serve as second micro-wire electrode 52micro-wires. Those first gap micro-wires 26 and second gap micro-wires56 that are located in both the first and second electrode gaps 60, 62are therefore dummy wires electrically isolated from both the first andsecond micro-wire electrodes 22, 52.

In one embodiment, the first or second gap micro-wires 26, 56 in thedummy-wire area 36 are located in the second layer 50 (as shown in FIGS.4C, 3E, and 3F), but in another embodiment are in the first layer 20. Inthe case in which an unpatterned conductive layer 30 is provided toelectrically connect the first micro-wires 24, the first or second gapmicro-wires 26, 56 in the dummy-wire area 36 are located in the secondlayer 50 to avoid electrically shorting the unpatterned conductive layer30.

By locating the second gap micro-wires 56 in the area of the firstmicro-wire electrodes 22 in a different layer from the other second gapmicro-wires 56 (those in the dummy-wire area 36), the conductivity ofthe first micro-wire electrodes 22 is improved. However, those secondgap micro-wires 56 in the area of the first micro-wire electrodes 22 donot then serve as electromagnetic interference shields as do the secondgap micro-wires in the dummy-wire area 36. Thus, the embodiment of FIG.4C compared to the embodiment of FIG. 3D represents a different tradeoffbetween electrode conductivity and electromagnetic interferenceshielding.

In an embodiment of the present invention, the first micro-wireelectrodes 22 are the drive electrodes of a capacitive touch screen andthe second micro-wire electrodes 52 are the sense electrodes of thecapacitive touch screen. Alternatively, the first micro-wire electrodes22 are the sense electrodes of a capacitive touch screen and the secondmicro-wire electrodes 52 are the drive electrodes of the capacitivetouch screen. The present invention includes a capacitive touch screenhaving the first and second micro-wire electrodes 22, 52 and first orsecond gap micro-wires 26, 56, as described above.

Referring to FIGS. 5 and 7, a method of making a micro-wire electrodestructure 5 of the present invention includes providing the substrate 10having the surface 12 in step 200. A first layer 20 is provided inrelation to the surface 12 in step 205 and a plurality of firstmicro-wire electrodes 22 spatially separated by first electrode gaps 60is located in the first layer 20 in step 210. Each first micro-wireelectrode 22 includes a plurality of electrically connected firstmicro-wires 24. A second layer 50 is provided in relation to the surface12 in step 215 and a plurality of electrically isolated secondmicro-wire electrodes 52 is located in the second layer 50 in step 220.The second layer 50 is at least partially different from the first layer20 and each second micro-wire electrode 52 includes a plurality ofelectrically connected second micro-wires 54. A gap layer 80 differentfrom the first layer 20 is provided in step 225 and a plurality of firstgap micro-wires 26 is located in each first electrode gap in step 230.At least some of the first gap micro-wires 26 are located in the gaplayer 80. The first gap micro-wires 26 are electrically isolated fromthe first micro-wires 24. As shown in FIG. 5, in an embodiment thesecond layer 50 and the gap layer 80 are the same layer and the step 215of providing the second layer 50 is the same as the step 225 ofproviding the gap layer 80. Moreover, at least some of the first gapmicro-wires 26 and the second micro-wires 54 are located in the samesecond layer 50 (and gap layer 80). In another embodiment, the step 220of locating the second micro-wires 54 is the same as step 230 oflocating the first gap micro-wires 26.

In additional embodiments of the present invention, a dielectric layer40 is provided between the first and second layer 20, 50. In anotherembodiment, a protective overcoat layer 70 is provided over the secondlayer 50 to protect the micro-wire electrode structure 5 of the presentinvention and provide a touch surface 11.

Referring to FIGS. 6 and 8, another method of making a micro-wireelectrode structure 5 of the present invention locates the first andsecond layers 20, 50 in an opposite order with respect to the surface12. Such an embodiment includes providing the substrate 10 having thesurface 12 in step 200. A second layer 50 is provided in relation to thesurface 12 in step 215 and a plurality of second micro-wire electrodes52 is located in the second layer 50 in step 250. Each second micro-wireelectrode 52 includes a plurality of electrically connected secondmicro-wires 54 and first gap micro-wires 26. A first layer 20 isprovided in relation to the surface 12 in step 205 and a plurality ofelectrically isolated first micro-wire electrodes 22 spatially separatedby first electrode gaps 60 is located in the first layer 20 in step 210.The first layer 20 is at least partially different from the second layer50 and each first micro-wire electrode 22 includes a plurality ofelectrically connected first micro-wires 24. The second layer 50 alsoserves as the gap layer 80 different from the first layer 20 andincludes the first gap micro-wires 26. The first gap micro-wires 26 areelectrically isolated from the first micro-wires 24. An optionalprotective overcoat layer 70 is provided over the second layer 50 toprotect the micro-wire electrode structure 5 and provide a touch surface11.

Referring to FIG. 5 again and to FIG. 9, another method of making amicro-wire electrode structure 5 of the present invention includesproviding the substrate 10 having the surface 12 in step 200. A firstlayer 20 is provided in relation to the surface 12 in step 205 and aplurality of first micro-wire electrodes 22 spatially separated by firstelectrode gaps 60 is located in the first layer 20 in step 210. Eachfirst micro-wire electrode 22 includes a plurality of electricallyconnected first micro-wires 24. An unpatterned conductive layer 30 isoptionally provided in electrical contact with the first micro-wireelectrodes 22 in step 260. In one embodiment, the first layer 20 islocated between the unpatterned conductive layer 30 and the surface 12(as shown in FIG. 5). In another embodiment, the unpatterned conductivelayer 30 is located between the first layer 20 and the surface 12 (notshown). In one embodiment, the unpatterned conductive layer 30 and firstlayer 20 are located between the second layer 50 and the surface 12 (asshown in FIG. 5). Alternatively, the second layer 50 is located betweenthe surface 12 and both the unpatterned conductive layer 30 and thefirst layer 20 (not shown, but FIG. 6 illustrates the second layer 50between the first layer 20 and the surface 12). In an embodiment, theunpatterned conductive layer 30 is used in the structure of FIG. 6, forexample by locating the unpatterned conductive layer 30 between thefirst layer 20 and the protective overcoat layer 70.

In yet another embodiment, an optional dielectric layer 40 is optionallylocated in contact with the unpatterned conductive layer 30 in step 270.In other embodiments, a portion of the first or second layers 20, 50serves to electrically isolate micro-wires in the first layer 20 frommicro-wires in the second layer 50 (e.g. as shown in FIG. 6). A secondlayer 50 is provided in relation to the surface 12 in step 215 and aplurality of second micro-wire electrodes 52 and first gap micro-wires26 are located in the second layer 50 in a common step 250.

Referring to FIG. 4C, FIG. 5, and to FIG. 10, in an alternativeembodiment a method of making a micro-wire electrode structure 5 of thepresent invention includes providing the substrate 10 having the surface12 in step 200. A first layer 20 is provided in relation to the surface12 in step 205 and a plurality of first micro-wire electrodes 22spatially separated by first electrode gaps 60 is located in the firstlayer 20 in step 280. Each first micro-wire electrode 22 includes aplurality of electrically connected first micro-wires 24 and at leastsome second gap micro-wires 56 located at the same time in the same step280. A second layer 50 is provided in relation to the surface 12 in step215 and a plurality of second micro-wire electrodes 52 spatiallyseparated by second electrode gaps 62 is located in the second layer 50in step 250. Each second micro-wire electrode 52 includes a plurality ofelectrically connected second micro-wires 54 and at least some first gapmicro-wires 26 located at the same time in the same step 250.

In useful embodiments of the present invention, in step 250 the secondmicro-wire electrodes 52 are formed in a single step in the second layer50 so that the second micro-wires 54 and first gap micro-wires 26 arelikewise formed in a single step and are formed from a common material.Likewise, in step 280 the first micro-wire electrodes 22 are formed in asingle step in the first layer 20 so that the first micro-wires 24 andsecond gap micro-wires 56 are formed in a single step and are formedfrom a common material.

In an embodiment, the unpatterned conductive layer 30 in electricalcontact with the first micro-wires 24 of the first micro-wire electrodes22 is provided before the second layer 50 is located. In otherembodiments of the present invention, the first layer 20 is located withrespect to the surface 12 before the second layer 50 is provided. Forexample, the first layer 20 is formed on the surface 12 and the secondlayer 50 is subsequently formed on the first layer 20, or on layers suchas the unpatterned conductive layer 30 or dielectric layer 40 formed onthe first layer 20, so that the first layer 20 is between the surface 12and the second layer 50. Alternatively, the second layer 50 is locatedwith respect to the surface 12 before the first layer 20 is provided.For example, the second layer 50 is formed on the surface 12 and thefirst layer 20 is subsequently formed on the second layer 50, or onlayers such as the unpatterned conductive layer 30 or dielectric layer40 formed on the second layer 50, so that the second layer 50 is betweenthe surface 12 and the first layer 20.

In a further embodiment of a method of the present invention, a displaysubstrate or a display cover having the surface 12 is provided so thatthe display cover or display substrate is the substrate 10.Alternatively, the substrate 10 is affixed to the display 110. In anembodiment, the display 110 is a source of electromagnetic radiation.

In yet another embodiment, the micro-wire electrode structure 5 ispeeled from the substrate 10 and applied to another substrate, such asthe display substrate or display cover. The micro-wire electrodestructure 5 is applied with either side adjacent to the other substrate,effectively enabling a reversal of layer order with respect to the othersubstrate. In such a structure, the end result is that the first andsecond micro-wires 24, 25 are effectively located at the bottom of theirrespective first and second layers 20, 50.

Referring to FIG. 14, the structure of FIG. 6 is constructed with theunpatterned conductive layer 30 in place of the overcoat layer 70 (FIG.6) in electrical contact with the first micro-wire electrodes 22 andfirst micro-wires 24 in first layer 20 separated by first electrode gaps60. The micro-wire electrode structure 5 is peeled from the surface 12of the substrate 10 (FIG. 6) and applied to another substrate (shown asthe display 110) with the unpatterned conductive layer 30 in contactwith the other substrate and the second layer 50 (also the gap layer 80)with second micro-wire electrodes 52 having second micro-wires 54 andfirst gap micro-wires 26 on the opposite side of the first layer 20.

In a useful embodiment that provides optical uniformity, the firstmicro-wire electrodes 22 are provided in a first micro-pattern that issimilar to a second micro-pattern in which the second micro-wires 54 areprovided but offset from the first micro-pattern in a direction parallelto the surface by a spatial phase difference of 180 degrees.

In various embodiments of the present invention, various layers areformed from a curable material, such as a polymer or resin that iscoated in a liquid form and then cured to form a solid, for example byexposure to ultra-violet radiation or heat. Curable materials caninclude cross-linking materials.

According to various embodiments of the present invention, micro-wiresare provided in association with layers in various ways. In oneembodiment, micro-wires are formed on a layer surface, for example byprinting on surface 12 and then coated with a curable layer that is thencured. In such an embodiment, the micro-wires are located at the bottomof the layer. In another embodiment, conductive ink is printed, forexample by inkjet, gravure, or flexographic printing, on top of a layersurface and then cured. Alternatively, micro-channels are imprinted inan uncured layer, the layer is cured, and then conductive ink suppliedin the micro-channels and cured to form micro-wires. In yet anothermethod, layers are laminated together. Laminated layers can includemicro-wires in a pre-formed pattern. Coating methods such as spincoating, curtain coating, slot coating, extrusion coating, and hoppercoating are known in the art as are printing methods such as ink jet,gravure, and flexographic printing. Lamination methods are well known.Conductive inks are also known as are method for imprinting and fillingmicro-channels.

First micro-wires 24 can extend partially or all of the way through thefirst layer 20. The unpatterned conductive layer 30 and the first layer20 can be the same common layer and first micro-wires 24 formed in, on,or under the common layer. The unpatterned conductive layer 30 and thefirst layer 20 can be coated together, for example with slot orextrusion coating. The first or second layers 20, 50 can be imprintedwith a stamp having protrusions as deep as or deeper than the depth ofthe respective layers. The unpatterned conductive layer 30 can be coatedon the first layer 20 and in contact with the first micro-wires 24. Inan embodiment, the first or second layers 20, 50 are cured to formmicro-channels that are filled with conductive ink and to form first orsecond micro-wires 24, 54. The dielectric layer 40, second layer 50, orovercoat layer 70 are also formed using known coating methods.

In embodiments of the present invention, the electrical resistance ofthe unpatterned conductive layer 30 is greater than the resistance ofeach of the first or second micro-wire electrodes 22, 52. In tests, theresistance of the unpatterned conductive layer 30 was measured as thesheet resistance of the unpatterned conductive layer 30 independently ofthe first or second micro-wires 24, 54. The resistance of the first orsecond micro-wire electrodes 22, 52 is the resistance measured along thelength of the first or second micro-wire electrodes 22, 52.

In an embodiment, the unpatterned conductive layer 30 has a sheetresistance greater than 1 kΩ per square, greater than 10 kΩ per square,greater than 100 kΩ per square, greater than 1 MΩ per square, greaterthan 10 MΩ per square, greater than 100 MΩ per square, greater than 1 GΩper square, greater than 10 GΩ per square, or greater than 100 GΩ persquare. This lower limit in resistivity of the unpatterned conductivelayer 30 is dependent in part on the frequency at which the first orsecond micro-wire electrodes 22, 52 are driven and on the touch-screencontroller 140 current and voltage characteristics and on theconductivity of the first or second micro-wire electrodes 22, 52.

In another embodiment, the resistance of the unpatterned conductivelayer 30 between any two first micro-wire electrodes 22 is at least fivetimes greater, at least ten times greater, at least twenty timesgreater, at least fifty times greater, at least 100 times greater, atleast 500 times greater, at least 1,000 times greater, at least 10,000,at least 100,000, or at least 1,000,000 times greater than theresistance of either of the any two first micro-wire electrodes 22. Inone embodiment, the resistance of the unpatterned conductive layer 30between the first micro-wire electrodes 22 separated by the firstelectrode gap 60 is at least ten times greater than the resistance ofany of the first micro-wire electrodes 22.

In a further embodiment of the present invention, the touch-screencontroller 140, for example an integrated circuit, for driving the firstmicro-wire electrodes 22 provides voltage and current to the firstmicro-wire electrodes 22 in a desired driver waveform having a periodand frequency. The frequency of the driver waveform limits the rate atwhich the capacitance between the first and second micro-wire electrodes22, 52 can be measured. Because the unpatterned conductive layer 30 iselectrically connected to the first micro-wire electrode 22 and has alimited conductivity, the rate at which the first micro-wire electrode22 and the unpatterned conductive layer 30 can be charged is likewiselimited. A micro-wire electrode, such as the first micro-wire electrode22, has open areas between the micro-wires in the micro-wire electrodethat, according to the present invention, are filled with conductivematerial in the unpatterned conductive layer 30. Thus, the conductivityof the unpatterned conductive layer 30 will define, in combination withthe open area defined by the geometry of the first micro-wires 24 in thefirst micro-wire electrode 22, the rate at which the first micro-wireelectrode 22 and the unpatterned conductive layer 30 can be charged ordischarged. Therefore, the conductivity of the unpatterned conductivelayer 30 and the open area define the time constant for charging ordischarging the first micro-wire electrode 22 and the center of the openarea in response to a voltage change as provided by the driver waveform.Therefore, according to the further embodiment of the present invention,the sheet resistance of the unpatterned conductive layer 30 issufficiently low that the time constant for charging the center of theopen area between first micro-wires 24 in the first micro-wire electrode22 is less than the period of a driver waveform. In another embodiment,the time constant is substantially less than the period. Bysubstantially less is meant at least 5% less, at least 10% less, atleast 20% less, or at least 50% less.

In operation, a touch-screen controller (for example touch-screencontroller 140 of FIG. 11) energizes one of the first micro-wireelectrodes 22 with a signal and senses one of the second micro-wireelectrode 52 to detect the capacitance or changes in capacitance of thearea overlapped by the one first micro-wire electrode 22 and one secondmicro-wire electrode 52. For such an application, the first micro-wireelectrodes 22 extending in a first direction parallel to the surface 12are located orthogonally to the second micro-wire electrodes 52extending in a second direction D2 parallel to the surface andorthogonal to the first direction D1.

Since the unpatterned conductive layer 30 electrically connects thefirst micro-wire electrodes 22, some current leaks from the driven firstmicro-wire electrode 22 to other first micro-wire electrodes 22.However, because the resistance of the unpatterned conductive layer 30is high relative to the resistance of the first micro-wire electrodes22, capacitance is still detected in the overlapped electrode area.Moreover, the presence of the unpatterned conductive layer 30 inhibitselectromagnetic interference from affecting the capacitance measure bythe second micro-wire electrode 52, especially if the electromagneticinterference originates from a side of the unpatterned conductive layer30 opposite the second micro-wire electrodes 52. Furthermore, theunpatterned conductive layer 30 assists in extending the electricalfield produced by driving the first micro-wires 24 in the one firstmicro-wire electrode 22 into the spaces between the first micro-wires24, thereby providing a more uniform field between the first micro-wireelectrode 22 and the second micro-wire electrode 52. A more uniformfield enables a more consistent and sensitive detection of capacitancechanges due to the presence of perturbing elements such as a finger or astylus at varying spatial locations. Furthermore, the presence of theunpatterned conductive layer 30 reduces the sensitivity of thetouch-screen device to differences in alignment between the micro-wiresof the first micro-wire electrodes 22 and the second micro-wireelectrodes 52.

In comparison to other prior-art solutions using a separate ground planebeneath driver or sensor electrodes to reduce the effect ofelectro-magnetic radiation, for example from a display located beneaththe touch screen, the present invention provides a thinner touch-screenand display structure with fewer layers.

A variety of techniques are usable to construct a touch screen device ofthe present invention. In various embodiments, the patterned firstmicro-wire electrodes 22 are formed in a layer, such as first layer 20,unpatterned conductive layer 30, or dielectric layer 40, printed ortransferred onto a layer, such as the substrate 10, unpatternedconductive layer 30, or dielectric layer 40, or laminated on thesubstrate 10 or other layer on the substrate 10. In other embodiments,the unpatterned conductive layer 30 is laminated, coated, formed byevaporation, sputtering, or chemical vapor deposition, or formed byatomic layer deposition on the first micro-wire electrodes 22 or firstlayer 20 or on the second layer 50. The dielectric layer 40 islaminated, coated, formed by evaporation, sputtering, or chemical vapordeposition, or formed by atomic layer deposition on the unpatternedconductive layer 30. The patterned second micro-wire electrodes 52 areformed in a layer, such as second layer 50 or dielectric layer 40,printed or transferred onto a layer, such as the substrate 10 ordielectric layer 40, or laminated on the substrate 10 or other layer onthe substrate 10.

In an embodiment, unpatterned conductive layer 30 or dielectric layer 40is deposited by sputtering or deposition and patterned outside thetouch-sensitive area 32 either with masks or by photolithographicprocesses. In an embodiment, conductive material is only deposited inthe touch-sensitive area 32. Alternatively, conductive material isdeposited over the entire substrate 10 and removed as needed, forexample in peripheral regions of the touch screen outside thetouch-sensitive area 32. In another embodiment, atomic layer depositionmethods are used to form a transparent conductive layer, for example apatterned aluminum zinc oxide layer using methods known in the art.Patterning outside the touch-sensitive area 32 is accomplished, forexample, by masking the deposition, using patterned depositioninhibitors, or by photolithographic processes.

In an embodiment, the substrate 10 and the surface 12 are provided instep 200, together with imprinting stamps. The first layer 20 isprovided on the substrate 10 and surface 12 in step 205, for example bycoating. The patterned first micro-wire electrodes 22 are formed byimprinting the first layer 20 with an imprinting stamp, curing the firstlayer 20 to form the first micro-channels that are filled withconductive ink. The conductive ink is cured to form first micro-wires 24and optional second gap micro-wires 56 located in the firstmicro-channels in step 210 or step 280. The unpatterned conductive layer30 is coated over the first micro-wires 24 in step 260 and the optionaldielectric layer 40 is optionally coated over the unpatterned conductivelayer 30 in step 270. The patterned second micro-wire electrodes 52 areformed by coating and imprinting the second layer 50 with an imprintingstamp, curing the second layer 50 to form second micro-channels that arefilled with conductive ink. The conductive ink is cured in step 250 toform the second micro-wires 54 and form the first gap micro-wires 26.

In other embodiments, imprinting methods are used to imprint firstmicro-channels in the dielectric layer 40 or in the unpatternedconductive layer 30. Similarly, in other embodiments imprinting methodsare used to imprint second micro-channels in the dielectric layer 40.

Printing methods are usable in other embodiments of the presentinvention. A conductive ink is printable, for example with aflexographic plate, on a substrate 10 or other layer and cured to formmicro-wires. Alternatively, a pattern of micro-wires is transferrable tothe substrate 10 or other layer from another substrate.

In an alternative embodiment, micro-wires are formed by coating aflexographic substrate having a raised pattern corresponding to adesired micro-wire pattern with a conductive ink. The flexographicsubstrate is brought into contact with a layer surface to print theconductive ink onto the layer surface. In an optional step, theconductive ink is dried. Flexographic substrates are known in theflexographic printing arts.

Transferred or printed micro-wires can be coated with curable materialto form the first layer 20 or second layer 50. The first layer 20 orsecond layer 50 can also be the dielectric layer 40. In an embodiment,the unpatterned conductive layer 30 is the first layer 20.

In yet another embodiment, layer structures are laminated to anotherlayer. For example, the first layer 20 is made as a separateconstruction (for example as a layer of PET) including first micro-wires24 and then laminated with an adhesive to substrate 10. Second layer 50is made and similarly laminated. The unpatterned conductive layer 30 ordielectric layer 40 can be laminated onto their respective layers,together or separately. In another embodiment, a layer structure isformed on a temporary substrate with a temporary adhesive on a firstside, the layer structure is permanently adhered to the substrate 10 orlayer formed on the substrate 10 on a second side, and then thetemporary substrate is removed from the first side, for example bypeeling.

In various embodiments, the unpatterned conductive layer 30 islaminated, coated, or deposited on the first micro-wire electrodes 22.In an embodiment, atomic layer deposition is used to form theunpatterned conductive layer 30. In other embodiments, the dielectriclayer 40 is laminated, coated, or deposited on the first micro-wireelectrodes 22.

Dielectric layer 40 can be any of many known dielectric materialsincluded polymers or oxides and are deposited or formed in any of avariety of known ways, including pattern-wise inkjet deposition,sputtering, or coating through a mask or blanket coated and patternedusing known photo-lithographic methods. Such known photo-lithographictechnology can include a photosensitive material that is opticallypatterned through a mask to cure the photosensitive material and removalof either the cured or the uncured material.

In an embodiment, unpatterned conductive layer 30 is transparent andincludes one or more of a variety of transparent conductive materials,for example organic conductive polymers such asPoly(3,4-ethylenedioxythiophene) (PEDOT),Poly(3,4-ethylenedioxythiophene) PEDOT: poly(styrene sulfonate) PSS,Poly(4,4-dioctylcyclopentadithiophene), and Polypyrrole (PPy),long-chain aliphatic amines (optionally ethoxylated) and amides,quaternary ammonium salts (such as, behentrimonium chloride orcocamidopropyl betaine), esters of phosphoric acid, polyethylene glycolesters, or polyols, polyaniline nanofibers, carbon nanotubes, graphene,metals such as silver nanowires, and inorganic conductive oxides such asITO, SnO₂, In₂O₃, ZnO, Aluminum-doped zinc oxide (AZO), CdO, Ga₂O₃,V₂O₅. Deposition methods for conductive materials can include solvent oraqueous coating, printing by for example inkjet, gravure, offset litho,flexographic, or electro-photographic, lamination, evaporation, chemicalvapor deposition (CVD), sputtering, atomic-layer deposition (ALD) orspatial-atomic-layer deposition (SALD).

In another embodiment, unpatterned conductive layer 30 is an ionicconductor, a solid ionic conductor, an electrolyte, a solid electrolyte,or a conductive gel, as are known in the art.

In an embodiment, the unpatterned conductive layer 30 has a thicknessless than or equal to 50 nm, 100 nm, 200 nm, 500 nm, or 1 micron. Inother embodiments, the unpatterned conductive layer 30 has a thicknessless than or equal to 10 microns, 100 microns, 200 microns, 500 microns,or 1 mm.

According to various embodiments of the present invention, the substrate10 is any material on which a layer is formed. The substrate 10 is arigid or a flexible substrate made of, for example, a glass, metal,plastic, or polymer material, is transparent, and can have opposingsubstantially parallel and extensive surfaces. The substrates 10 caninclude a dielectric material useful for capacitive touch screens andcan have a wide variety of thicknesses, for example 10 microns, 50microns, 100 microns, 1 mm, or more. In various embodiments of thepresent invention, substrates 10 are provided as a separate structure orare coated on another underlying substrate, for example by coating apolymer substrate layer on an underlying glass substrate.

In various embodiments the substrate 10 is an element of other devices,for example the cover or substrate of a display or a substrate, cover,or dielectric layer of a touch screen. In an embodiment, the substrate10 of the present invention is large enough for a user to directlyinteract therewith, for example using an implement such as a stylus orusing a finger or hand. Methods are known in the art for providingsuitable surfaces on which to coat or otherwise form layers. In a usefulembodiment, the substrate 10 is substantially transparent, for examplehaving a transparency of greater than 90%, 80% 70% or 50% in the visiblerange of electromagnetic radiation.

Electrically conductive micro-wires and methods of the present inventionare useful for making electrical conductors and buses for transparentmicro-wire electrodes and electrical conductors in general, for exampleas used in electrical buses. A variety of micro-wire patterns are usedand the present invention is not limited to any one pattern. Micro-wirescan be spaced apart, form separate electrical conductors, or intersectto form a mesh electrical conductor on, in, or above the substrate 10.Micro-channels can be identical or have different sizes, aspect ratios,or shapes. Similarly, micro-wires can be identical or have differentsizes, aspect ratios, or shapes. Micro-wires can be straight or curved.

A micro-channel is a groove, trench, or channel formed on or in a layerextending from the surface of the layer and having a cross-sectionalwidth for example less than 20 microns, 10 microns, 5 microns, 4microns, 3 microns, 2 microns, 1 micron, or 0.5 microns, or less. In anembodiment, the cross-sectional depth of a micro-channel is comparableto its width. Micro-channels can have a rectangular cross section. Othercross-sectional shapes, for example trapezoids, are known and areincluded in the present invention. The width or depth of a layer ismeasured in cross section. Micro-channels are not distinguished in theFigures from the micro-wires.

Imprinted layers useful in the present invention can include a curedpolymer material with cross-linking agents that are sensitive to heat orradiation, for example infra-red, visible light, or ultra-violetradiation. The polymer material is a curable material applied in aliquid form that hardens when the cross-linking agents are activated.When a molding device, such as an imprinting stamp having an inversemicro-channel structure is applied to liquid curable material and thecross-linking agents in the curable material are activated, the liquidcurable material in the curable layer is hardened into a cured layerwith imprinted micro-channels. The liquid curable materials can includea surfactant to assist in controlling coating. Materials, tools, andmethods are known for embossing coated liquid curable materials to formcured layers.

A cured layer is a layer of curable material that has been cured. Forexample, a cured layer is formed of a curable material coated orotherwise deposited on a layer surface to form a curable layer and thencured to form the cured layer. The coated curable material is consideredherein to be a curable layer before it is cured and cured layer after itis cured. Similarly, a cured electrical conductor is an electricalconductor formed by locating a curable material in micro-channel andcuring the curable material to form a micro-wire in a micro-channel. Asused herein, curing refers to changing the properties of a material byprocessing the material in some fashion, for example by heating, drying,irradiating the material, or exposing the material to a chemical,energetic particles, gases, or liquids.

The curable layer is deposited as a single layer in a single step usingcoating methods known in the art, such as curtain coating. In analternative embodiment, the curable layer is deposited as multiplesub-layers using multi-layer deposition methods known in the art, suchas multi-layer slot coating, repeated curtain coatings, or multi-layerextrusion coating. In yet another embodiment, the curable layer includesmultiple sub-layers formed in different, separate steps, for examplewith a multi-layer extrusion, curtain coating, or slot coating machineas is known in the coating arts.

Curable inks useful in the present invention are known and can includeconductive inks having electrically conductive nano-particles, such assilver nano-particles. In an embodiment, the electrically conductivenano-particles are metallic or have an electrically conductive shell.The electrically conductive nano-particles can be silver, can be asilver alloy, or can include silver. In various embodiments, cured inkscan include metal particles, for example nano-particles. The metalparticles are sintered to form a metallic electrical conductor. Themetal nano-particles are silver or a silver alloy or other metals, suchas tin, tantalum, titanium, gold, copper, or aluminum, or alloysthereof. Cured inks can include light-absorbing materials such as carbonblack, a dye, or a pigment.

Curable inks provided in a liquid form are deposited or located in firstor second micro-channels and cured, for example by heating or exposureto radiation such as infra-red radiation, visible light, or ultra-violetradiation. The curable ink hardens to form the cured ink that makes upfirst or second micro-wires 24, 54. For example, a curable conductiveink with conductive nano-particles are located within first or secondmicro-channels and cured by heating or sintering to agglomerate or weldthe nano-particles together, thereby forming an electrically conductivefirst or second micro-wire 24, 54. Materials, tools, and methods areknown for coating liquid curable inks to form micro-wires.

In an embodiment, a curable ink can include conductive nano-particles ina liquid carrier (for example an aqueous solution including surfactantsthat reduce flocculation of metal particles, humectants, thickeners,adhesives or other active chemicals). The liquid carrier is located inmicro-channels and heated or dried to remove liquid carrier or treatedwith hydrochloric acid, leaving a porous assemblage of conductiveparticles that are agglomerated or sintered to form a porous electricalconductor in a layer. Thus, in an embodiment, curable inks are processedto change their material compositions, for example conductive particlesin a liquid carrier are not electrically conductive but after processingform an assemblage that is electrically conductive.

Once deposited, the conductive inks are cured, for example by heating.The curing process drives out the liquid carrier and sinters the metalparticles to form a metallic electrical conductor. Conductive inks areknown in the art and are commercially available. In any of these cases,conductive inks or other conducting materials are conductive after theyare cured and any needed processing completed. Deposited materials arenot necessarily electrically conductive before patterning or beforecuring. As used herein, a conductive ink is a material that iselectrically conductive after any final processing is completed and theconductive ink is not necessarily conductive at any other point in themicro-wire formation process.

In various embodiments of the present invention, micro-channels ormicro-wires have a width less than or equal to 10 microns, 5 microns, 4microns, 3 microns, 2 microns, or 1 micron. In an example andnon-limiting embodiment of the present invention, each micro-wire isfrom 10 to 15 microns wide, from 5 to 10 microns wide, or from 5 micronsto one micron wide. In some embodiments, micro-wires can fillmicro-channels; in other embodiments micro-wires do not fillmicro-channels. In an embodiment, the micro-wires are solid; in anotherembodiment, the micro-wires are porous.

Micro-wires can be metal, for example silver, gold, aluminum, nickel,tungsten, titanium, tin, or copper or various metal alloys including,for example silver, gold, aluminum, nickel, tungsten, titanium, tin, orcopper. Micro-wires can include a thin metal layer composed of highlyconductive metals such as gold, silver, copper, or aluminum. Otherconductive metals or materials are usable. Alternatively, micro-wirescan include cured or sintered metal particles such as nickel, tungsten,silver, gold, titanium, or tin or alloys such as nickel, tungsten,silver, gold, titanium, or tin. Conductive inks are used to formmicro-wires with pattern-wise deposition or pattern-wise formationfollowed by curing steps. Other materials or methods for formingmicro-wires, such as curable ink powders including metallicnano-particles, are employed and are included in the present invention.

Electrically conductive micro-wires of the present invention areoperable by electrically connecting micro-wires through connection padsand electrical connectors to electrical circuits that provide electricalcurrent to micro-wires and can control the electrical behavior ofmicro-wires. Electrically conductive micro-wires of the presentinvention are useful, for example in touch screens such asprojected-capacitive touch screens that use transparent micro-wireelectrodes and in displays. Electrically conductive micro-wires can belocated in areas other than display areas, for example in the perimeterof the display area of a touch screen, where the display area is thearea through which a user views a display.

Inventive Example:

The second micro-wire electrodes 52 including the second micro-wires 54but excluding the first gap micro-wires 26 were prepared using astandard lithographic process. Microposit 1813 photoresist wasspin-coated onto a 1000 Å thermally deposited aluminum layer coated on a2.5 inch by 2.5 inch square 4 mil PET support. The photoresist wasexposed to UV light through a chrome-on-quartz mask, developed, rinsedand dried. The film was then etched in PAN etch leaving a positive imagehaving 10 μm wide aluminum micro-wires forming connected openright-angle-diamond electrodes, 1600 μm on diagonal. The periodic widthof the second micro-wire electrodes 52 was 6.42 mm separated by 400micron micro-wire breaks 64 in the second micro-wires 54 atintersections between the second micro-wire electrodes 52. The secondmicro-wire electrodes 52 were terminated with conductive rectangularpads to enable simple resistance measurements end-to-end. The pads atone end of the second micro-wire electrodes 52 also had conductive buslines leading to additional pads at the edge of the support (thedielectric layer 40) to enable conventional 1 mm pitch edge connectionwith electrical test fixtures. The photoresist was removed with acetoneand methanol baths and dried with nitrogen. The second micro-wireelectrode 52 resistance was measured to be on the order of 450Ω fromend-to-end and essentially infinite between nearest neighbor electrodes.

The first micro-wire electrodes 22 including the first micro-wires 24but excluding the second gap micro-wires 56 were prepared as were thesecond micro-wire electrodes 52, on a separate 4 mil PET support(substrate 10), and with the final addition of a transparent unpatternedconductive layer 30 formed on the lithographically patterned firstmicro-wires 24 by spin coating a solution of PEDOT/PSS at 3000 rpm anddrying on a hotplate for 2 minutes at 110° C. Sheet resistance of thedried PEDOT/PSS coating on a section of bare PET support using afour-point probe was 8 MΩ/square. First electrode resistance wasmeasured to be on the order of 450Ω from end-to-end with approximately160 kΩ between nearest neighbor electrodes. Thus the ratio of shortingresistance to first electrode resistance in this inventive example was356 to 1.

A functional touch-screen was fabricated from the prepared second andfirst micro-wire electrodes 52, 22 by first laminating a cover sheet of4 mil PET (overcoat layer 70) on the exposed side of the secondmicro-wire electrodes 52 on dielectric layer 40 using optically clearadhesive, OCA (Adhesives Research, ARClear 8154 Optically ClearUnsupported Transfer Adhesive) to form a coversheet (overcoat layer 70)of the touch-screen example. The second micro-wire electrodes 52 wereoriented 90 degrees with respect to the first micro-wire electrodes 22and offset such that the intersections of the diamonds were directlyabove the center of the diamonds of the first micro-wire electrodes 22.The uncoated side of the dielectric layer 40 was laminated to theexposed side of the unpatterned conductive layer 30 using the sameoptically clear adhesive. The dielectric thus includes both the OCA andthe 4 mil PET dielectric layer 40.

Comparative Example

For the purpose of comparison, a control touch-screen representing anexample of the prior art was prepared exactly as described above exceptthe coating of PEDOT/PSS forming the unpatterned conductive layer 30 waseliminated in the comparative example.

Results:

The measurement apparatus included two translation stages which wereused to move a mechanical, artificial finger incrementally across thesample. The weight of the finger was used to provide a constant touchforce and the tip of the artificial finger included a compliant,conductor loaded, polymer foam mounted on the end of a conductive rod.All but one first micro-wire electrode 22 were held at ground while avoltage waveform including a controlled burst of sine waves (either 100kHz or 1 MHz) was applied to one of the first micro-wire electrodes 22.All of the second micro-wire electrodes 52 were held at ground and onewas connected to a charge sensitive pre-amplifier (operational amplifierwith capacitor feedback) which held the second micro-wire electrodes 52at ground and output a voltage proportional to the input charge. Theoutput voltage from the sensing amplifier was sampled periodically at 20MHz. Digital processing was used to synchronously (with respect to thedriven waveform) rectify the sampled signal and compute an average (inphase) voltage. By spatially stepping the artificial finger across thesample in a spatial matrix of locations, the sensed voltages are mappedas a function of the artificial finger location. By inference, theresponse of a single repetitive unit at a single location is the same asthe response at any other location (except for boundaries). By measuringa known conventional capacitor with the same instrument, the voltagereading is converted to effective capacitance readings.

The mutual no-touch capacitance for the inventive example was 1.8 timeshigher than the comparative example at either 100 kHz or 1 MHz. Thisincrease illustrates the effective field-spreading characteristic of theunpatterned conductive layer 30 in the inventive example at practicalmeasurement frequencies and is usable to reduce the relative powerconsumption of a touch-sensor controller resulting in improved systemefficiency.

To test touch sensitivity, the examples were scanned with a 10.4 mmdiameter artificial finger in a matrix pattern centered at anintersection of the active second and first micro-wire electrodes 52,22. In each case, far from the intersection, the capacitance wasequivalent to the no-touch condition, as expected. Centered on theintersection the capacitance was less than the no-touch condition andthe relative difference between the near node touch and no-touch readingwas taken as a measure of the touch sensitivity.

Touch-Sensitivity=−(C _(touch) −C _(no) _(—) _(touch))/C _(no) _(—)_(touch)

At 1 MHz the relative touch sensitivity was 42% for the inventiveexample and 50% for the comparative example. Thus, the touch signal inthe inventive example was strong and differences between the inventiveand comparative example small, demonstrating that the unpatternedconductive layer 30 has minimal effect on the touch sensitivity whileincreasing the capacitance. The observed difference in touch sensitivitycan be due in part or entirely to imperfections of the alignment ofdriver and sensor electrodes (first and second micro-wire electrodes 22,52) in each example.

To test the shielding properties, connections to the second and firstmicro-wire electrodes 52, 22 were exchanged thus reversing the roles ofthe first and second micro-wire electrodes 22, 52 and the artificialfinger was scanned over the back-side of the examples. By symmetry thismakes no difference for the comparative example but shows a reduction intouch sensitivity due to the shielding effects of the field-spreadingunpatterned conductive layer 30 in the inventive example. Indeed, theresults showed a factor of 3 reductions in touch sensitivity at 1 MHzand complete elimination of touch signal at 100 kHz for the inventiveexample. This reduction in frequency response is an illustration of thetime constant for charging or discharging the open areas of theunpatterned conductive layer 30 in the first micro-wire electrode 22.Touch sensitivity of the comparative example was unaffected, asexpected. Thus the field spreading unpatterned conductive layer 30 inthe inventive example exhibited highly effective shielding at practicalfrequencies with no deleterious effects due to electrical shortingbetween first micro-wire electrodes 22. Capacitance signal increased andlittle change in touch sensitivity was observed when driven and sensedin the intended configuration achieving a considerable improvement inoverall system efficiency relative to the prior art example wasdemonstrated.

Methods and devices for forming and providing substrates and coatingsubstrates are known in the photo-lithographic arts. Likewise, tools forlaying out electrodes, conductive traces, and connectors are known inthe electronics industry as are methods for manufacturing suchelectronic system elements. Hardware controllers for controlling touchscreens and displays and software for managing display and touch screensystems are well known. These tools and methods are usefully employed todesign, implement, construct, and operate the present invention.Methods, tools, and devices for operating capacitive touch screens areused with the present invention.

In addition to the inventive and comparative examples described, atouch-screen structure of the present invention having a PEDOT/PSSunpatterned conductive layer 30 was constructed using the imprintingtechniques described and, in a separate sample, an unpatternedconductive layer 30 of AZO on etched first micro-wires 24 was formedusing atomic-layer deposition methods.

The first or second micro-wire electrodes 22, 52 can be formed in avariety of patterns. Electrodes can be rectangular and arranged inregular arrays. The first micro-wire electrodes 22 and the secondmicro-wire electrodes 52 can be arranged orthogonally to each other.Alternatively, electrodes can be arranged using polar coordinates, incircles, or in other curvilinear patterns. Electrodes can have uniformspacing or widths. Alternatively, electrodes can have non-uniformspacing and variable widths.

The present invention is useful in a wide variety of electronic devices.Such devices can include, for example, photovoltaic devices, OLEDdisplays and lighting, LCD displays, plasma displays, inorganic LEDdisplays and lighting, electrophoretic displays, electrowettingdisplays, dimming mirrors, smart windows, transparent radio antennae,transparent heaters and other touch-screen devices such as capacitivetouch screen devices.

The invention has been described in detail with particular reference tocertain embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

PARTS LIST

-   P direction-   D1 direction-   D2 direction-   5 micro-wire electrode structure-   10 substrate-   11 touch surface-   12 surface-   20 first layer-   22 first micro-wire electrode-   24 first micro-wire-   26 first gap micro-wires-   30 unpatterned conductive layer-   32 touch-sensitive area-   36 dummy-wire area-   40 dielectric layer-   50 second layer-   52 second micro-wire electrode-   54 second micro-wire-   56 second gap micro-wires-   60 first electrode gap-   62 second electrode gap-   64 micro-wire breaks-   70 overcoat layer-   80 gap layer-   100 display and touch-screen apparatus-   110 display-   120 touch screen-   122 first transparent substrate-   124 dielectric layer-   126 second transparent substrate-   128 touch pad area

PARTS LIST (CON'T)

-   130 first electrode-   132 second electrode-   134 wires-   136 electrical bus connections-   140 touch-screen controller-   142 display controller-   150 micro-wire-   152 dummy micro-wires-   156 micro-pattern-   200 provide substrate surface step-   205 provide first layer step-   210 locate first micro-wires step-   215 provide second layer step-   220 locate second micro-wires step-   225 provide gap layer step-   230 locate gap micro-wires step-   250 locate second micro-wires and first gap micro-wires step-   260 provide unpatterned conductive layer step-   270 locate dielectric layer step-   280 locate first micro-wires and second gap micro-wires step

1. A method of making a micro-wire electrode structure, comprising:providing a substrate having a surface; locating a plurality of firstmicro-wire electrodes spatially separated by first electrode gaps in afirst layer in relation to the surface, each first micro-wire electrodeincluding a plurality of electrically connected first micro-wires;locating a plurality of electrically isolated second micro-wireelectrodes in a second layer in relation to the surface, the secondlayer at least partially different from the first layer and each secondmicro-wire electrode including a plurality of electrically connectedsecond micro-wires; and locating a plurality of first gap micro-wires ineach first electrode gap, at least some of the first gap micro-wireslocated in a gap layer different from the first layer, the first gapmicro-wires electrically isolated from the first micro-wires.
 2. Themethod of claim 1, further including locating an unpatterned conductivelayer in electrical contact with the first micro-wires of the firstmicro-wire electrodes.
 3. The method of claim 1, further includinglocating at least some of the first gap micro-wires and locating atleast some of the second micro-wires in the second layer in a commonstep so that the at least some of the first gap micro-wires are withinthe second micro-wire electrodes and are electrically connected to thesecond micro-wires.
 4. The method of claim 1, further includingspatially separating the second micro-wire electrodes by secondelectrode gaps and locating a plurality of second gap micro-wires ineach second electrode gap, the second gap micro-wires electricallyisolated from the second micro-wires.
 5. The method of claim 4, furtherincluding locating at least some of the second gap micro-wires and atleast some of the first gap micro-wires in a common layer parallel tothe surface in a common step.
 6. The method of claim 5, furtherincluding locating at least some of the second gap micro-wires andlocating at least some of the first gap micro-wires in a common step inthe first layer and the first layer is the common layer.
 7. The methodof claim 6, further including locating the second micro-wires andlocating at least some of the first gap micro-wires within the secondmicro-wire electrodes and electrically connected to the secondmicro-wires in a common step.
 8. The method of claim 6, furtherincluding locating the second gap micro-wires and locating at least someof the first gap micro-wires within the second electrode gap andelectrically connected to the second gap micro-wires in a common step.9. The method of claim 1, further including locating the first layerbetween the second layer and the surface and before the second layer islocated.
 10. The method of claim 9, further including providing anunpatterned conductive layer in electrical contact with the firstmicro-wires of the first micro-wire electrodes before the second layeris located.
 11. The method of claim 9, further including driving thefirst micro-wire electrodes with a signal and sensing the secondmicro-wire electrodes to provide a signal for a capacitive touch screen.12. The method of claim 1, further including locating the second layerbetween the first layer and the surface before the first layer islocated.
 13. The method of claim 12, further including driving thesecond micro-wire electrodes with a signal and sensing the firstmicro-wire electrodes to provide a signal for a capacitive touch screen.14. The method of claim 1, further including providing a displaysubstrate or a display cover having the surface or affixing thesubstrate to a display and wherein the display is the source ofelectromagnetic radiation.
 15. The method of claim 1, further includinglocating the first micro-wire electrodes extending in a first directionparallel to the surface and locating the second micro-wire electrodesextending in a second direction parallel to the surface.
 16. The methodof claim 15, wherein the first direction is orthogonal to the seconddirection.
 17. The method of claim 15, further including forming a firstpattern with the first micro-wires, and forming a second pattern similarto the first pattern with the second micro-wires.
 18. The method ofclaim 17, wherein the first pattern is spatially offset from the secondpattern in a direction parallel to the surface by a phase difference of180 degrees.
 19. The method of claim 1, further including locating thefirst micro-wire electrodes so that the first micro-wire electrodes areelectrically isolated.